(Reuters) - Royal Caribbean Cruises Ltd (RCL.N) said on Thursday it would buy a 66.7 percent stake in privately owned Silversea Cruises for about $1 billion to add ultra-luxury and expedition cruises to its fleet.

FILE PHOTO - A view of the world's largest cruise ship of Royal Caribbean Cruises, the 362-metre-long Symphony of the Seas, during its world presentation ceremony, berthed at a port in Malaga, Spain March 27, 2018. REUTERS/Jon Nazca

Silversea Cruises, which has nine ships, sails to destinations including Antarctica, the Arctic and Greenland, with most of its tickets selling for more than $5,000.

In contrast, the most expensive cruises run by Royal Caribbean under its Azamara Club Cruises brand cost around $3,000.

“Ultraluxury and expedition cruises are gaps in our portfolio today,” Royal Caribbean Chief Executive Officer Richard Fain said on a conference call.

The two segments are the fastest growing areas in the industry that the company could not develop on its own, Fain added in an interview with Reuters.

Shares of the U.S. cruise operator rose as much as 7 percent to $115.50, with the company also maintaining its full-year profit forecast despite higher fuel prices and a stronger dollar.

Including debt, the deal is valued at $2 billion. Royal Caribbean said it plans to finance the purchase through debt.

The 2018 total worldwide ocean cruise industry is estimated to reach $45.6 billion in revenue, a 4.6 percent increase over 2017, according to the industry analytics firm Cruise Market Watch. Royal Caribbean had nearly $9 billion in revenue at the end of 2017.

Silversea Chairman Manfredi Lefebvre d’Ovidio will get about 472,000 Royal Caribbean shares, payable after the Miami-based company achieves some 2019-2020 performance targets.

This translates to about $51 million, based on Royal Caribbean’s closing price on Wednesday.

“Silversea had a fantastic plan of growing on its own, but I did realize that the potential that the market was offering Silversea was beyond the means that I could put in place,” Lefebvre d’Ovidio told Reuters.

Royal Caribbean does not expect the transaction, which will likely close later in the year, to materially impact its near-term adjusted earnings per share, the company said.